Technical Field
The present disclosure relates to a graphene oxide free-standing film, a method of making the film, and a method of using the film to shield electromagnetic radiation, especially at microwave frequencies from 1 GHz to 12 GHz.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, is neither expressly or impliedly admitted as prior art against the present invention.
Electromagnetic radiation emitted by electrical and electronic devices not only reveals sensitive information about the devices, but also interferes with their operation and inflicts various health hazards on exposed individuals, particularly when the electromagnetic radiation is at microwave frequencies from 300 MHz to 300 GHz. In fact, the World Health Organization has confirmed that exposure to microwave radiation could increase the risk of brain cancer. As a result, various shielding materials have been developed, including metals, conductive ceramic sheetings, and graphene or carbon nanotubes, however, they are heavy, expensive, and/or prone to corrosion and leakage of radiation. Further, as microwave radiation becomes more energetic at higher frequencies, e.g. above 8 GHz, and thus more harmful to exposed individuals, the radiation leakage exhibited by those shielding materials becomes more severe.
It therefore would be useful to provide compositions and methods for effectively shielding electromagnetic radiation, particularly at microwave frequencies, wherein the compositions are relatively light, corrosion resistant and flexible, and can be provided and incorporated into devices and/or existing shielding materials at relatively low cost. Graphene oxide is a compound of carbon oxygen, and hydrogen in variable ratios, obtained by treating graphite with strong oxidizers. The oxidized bulk product is a yellow solid with C/O ratio between 2.1 and 2.9, that retains the layer structure of graphite but with a much larger and irregular spacing.
Graphene oxide is hydrophilic and can be dispersed in water. When sifted out of the dispersion (as in paper manufacture) and dried, solid graphene oxide forms an exceedingly strong free-standing graphene oxide film comprising stacked layers of graphene oxide nanosheets.
The structure and properties of graphene oxide depend on the particular synthesis method and degree of oxidation, however, the graphene oxide structure typically preserves the layer structure of the parent graphite.